Project III: Vpr/GR (Aim lla) Project Leader: Velpandi Ayyavoo, PhD Vpr is involved in nuclear localization and trafficking of the provirus into the nucleus of non-dividing cells, such as macrophages and dendritic cells244'245. Though Vpr is not absolutely essential for T cell infection, the presence of Vpr enhances viral replication in T cells and activates latently infected and resting T cells. Vpr enhances viral replication by altering transport into the nucleus and by facilitating changes in cellular functions and the HIV-1 life cycle246. Virion-associated Vpr transactivates HIV-1 long terminal repeat sequences (LTR) and activates virus transcription prior to de novo synthesis of other viral proteins through an interaction with glucocorticoid receptor (GR). Recent studies using Vpr mutants by us and other investigators have clearly demonstrated that Vpr interacts with GR through a highly conserved leucine-rich GR signature motif in Vpr, suggesting that the Vpr/GR interaction is specific129' . Furthermore, Vpr/GR interaction and its subsequent functional regulations are independent of other Vpr functions such as cell cycle arrest. This suggests a possible role for the GR pathway in Vpr-mediated virus replication. In work done by our laboratory, the cellular dysregulation by Vpr was found to relate to the ability of Vpr to suppress NF-kB activity through the induction of IkB transcription in a manner similar to glucocorticoids248. The regulation of NF-kB by Vpr suggests a molecular basis for the cellular effects of Vpr and supports the possibility that this gene product might mediate some aspects of viral pathogenesis. Taken together, these results suggest that Vpr, via the GR pathway, could, in part, contribute to viral replication and disease progression. Toward accomplishing Aim Ha, Project III will work closely with the Cellular and Single Particle Imaging Core to further characterize the interaction between Vpr and GR in cells and will begin expression studies to identify methods and domains of the GR protein most suitable for structural determination.